The present invention concerns deep-acting, soil-loosening gang plows used to loosen and break up compacted soils, usually for agricultural purposes, such plows being provided with a frame adjustably mounted on a towing vehicle, and furthermore being provided with power-driven shares that perform the functions of cutting free the bottom of a furrow slice interval and then lifting the material thereof in order to break up and loosen the same, the shares being mounted on downwardly extending teeth which are adjustable with respect to their depth of penetration into the subsoil.
In agriculture it has for years been known to use soil loosening plows to improve soil quality and increase harvestable yield. Initially these devices were provided with immovable, downwardly extending teeth having blades or shares thereon. Nowadays, these soil-loosening plows are frequently provided with blades that perform movements during plowing, in order to improve the quality of the loosening action, on the one hand, and, on the other hand, to reduce the required towing power or, equivalently, to increase the acreage worked per unit time in the event that the towing power is a given. In agriculture, these soil-loosening gang plows are attached to the rear of a towing vehicle because, if located there, they are very easily maneuvered. Now that it is known that blades or shares which perform movements during plowing can decrease the required towing force, various new systems have been developed to cause the blades or shares to perform such movements.
DE-OS 1,918,670 discloses a system in which the blade rocks about a pivot pin that extends transverse to the blade advancement direction. DE-PS 2,607,364.3 discloses another system, in which the blade is moved by two levers of a linkage arrangement, in such a manner as to perform a compound motion constituted by two individual motions: the first, a forward penetration serving to cut free the bottom of a furrow slice increment; followed by the second, a lifting action which breaks up and loosens the material of the furrow slice. DE-OS 3,128,736.0 discloses a further system, in which a rocking motion is positively imparted to the blade as a result of the conjoined motions performed by the tooth that carries this blade and performed by an auxiliary cutter pivotally connected to the blade.
Each of the last two mentioned systems has one single movable blade per furrow to be formed, such single blade constituting the whole of the share and being positively driven throughout its entire cycle of motion in such a manner that, during the course of one rotation of a crank, material is displaced first by the leading half of the blade and then by the trailing half of the blade.
The leading half of the blade, at its leading end, cuts free the bottom of a furrow slice interval during a forwardly directed cutting motion. The trailing blade half lifts the material of the furrow slice during a subsequent lifting step. For this purpose, the levers which carry and impart motion to the blades are provided with corresponding, special linkages linking them together. These linkages require a certain amount of space underneath the blade halves, this being due to: the need to brace the blade against the soil resistance presented to it; the need to provide encapsulated bearings able to withstand chemically aggressive soils; and being also due to the geometry selected for the polygonal linkage itself. For this reason, in such constructions so large a blade surface is required that, when the blade is designed with a suitable shape, the result is a very large-bladed and very power-consuming soil-loosening plow that can be towed only by a correspondingly powerful towing vehicle. For practical purposes, and taking into account the towing forces provided by the towing vehicles generally available in agriculture a significant compromise had to be made hitherto, with regard to the design of the blade or share. Mounting and bearing considerations dictated blade designs such that the power required for cutting free the bottom of the furrow slice differed very markedly from the power required for lifting up the material of the furrow slice. Since the towing-force required of the towing vehicle depends upon the peak towing force required, which here is that required during the initial step of cutting free the bottom of the furrow slice, wheeled farm vehicles of the type having vehicle tires would repeatedly lose traction. Thus, hitherto, these plows, if designed with share or blade motions of an actually worthwhile character, would for most practical purposes be used only with caterpillar-type towing vehicles. The latter, however, are only seldom available in agriculture, for which reason deep-acting soil-loosening gang plows with optimum blade motion could not find wide application.
DE-OS 3,006,446 discloses a tractor-mounted device for loosening soil having two soil-loosening tools movable up and down on a carrier frame, being arranged one behind the other as a pair, the front such loosening tool being located higher than the rear such tool, considered in the direction of tractor travel, and the shafts for the two tools of each such pair of tools moving up and down in phase-opposition to each other. The leading end of the rear tool and the trailing end of the front lie advantageously on a straight line extending approximately in the direction of the up and down motion of the tools. The shafts for the tools can be arranged inclined upwardly and forwardly, with their motions being performed in the direction of their elongation. In particular, the front soil-loosening tool must have a wider blade than the more deeply positioned rear tool. The shafts for these tools are mounted to be longitudinally displaceable. Each tool of the pair can be pivotally mounted on a respective two-armed lever and be moved by means of an eccentric drive having a vibrating output shaft that extends transverse to the direction of travel. With this device the upper soil layer is first to be broken up by the front tool and then be more finely broken up as the underlying soil layer is lifted by the more deeply positioned rear tool, so that with two blades or shares working one behind the other at different depths there remain no compacted intermediate layer. With the two blades or shares being located at different depths and moving up and down in phase-opposition to each other, a shearing action is intended to develop in the soil between them, such that, in the space between them, the crumbled portions of the material of the deeper layer be rubbed against one another. Even in the earlier-mentioned case where the shafts for the two tools of a pair are inclined, so that the paths of motion of the two shares are likewise inclined, the motions performed by the two shares do not include any significant horizontal component, since only motion predominantly in the vertical direction is contemplated. Accordingly, as to any forward motion performed by the shares in such system (and ignoring whatever forward motion results from the mere fact of forward tractor travel), there is no essential difference compared to systems having entirely stationary shares, in so far as one is concerned with share behavior during the initial step of cutting free the bottom of a furrow slice, which in this prior-art system means the upper layer of the furrow slice. Additionally, this known construction exhibits certain disadvantages. Theoretically, this construction is meant to operate with improved quietness. However, in this respect it fails adequately to take into account the fact that the two shares, when positively forced down by the eccentric drive mechanism, strike with their substantially flat bottom faces against compacted and growth-covered soil, this leading to considerable unevenness of operation. Also, due to the significantly different lengths of the shafts for the two tools, it is in such a construction difficult to provide simple, inexpensive and yet effective mass equalization such as could present to the prime mover, during the course of one cycle of operation of the eccentric drive mechanism, an approximately uniform load for the prime mover to drive Furthermore, both of the two shares must operate in not yet loosened soil. The two shares do not together form a compound or composite plowshare structure whose two parts perform markedly different functions, but instead the two shares perform essentially the same functions and merely operate at different depths. The shafts for the two tools, located one behind the other, do both extend through the upper layer, but do not both extend into the region of the lower layer, which would be essential for the type of deep subsoil loosening action here in question. The shafts and their shares operate, essentially, like a deep-acting soil-loosening plow of the type having stationary shares and share-carrying teeth, to which however a certain amount of up and down motion is imparted, but without any operational or functional subdivision into a first step in which the bottom of a furrow slice interval is cut free, alternating with a subsequent second step in which the material of the furrow slice is lifted. Accordingly, it is not possible to achieve the advantages of the earlier-mentioned DE-PS 2,607,364 and DE-OS 3,128,736, such as those regarding a decreased power requirement even when working in difficult soils.
British patent 1,292,844 discloses an earth-working machine which forms a subsurface channel and simultaneously lays a cable into such channel. A special feature of this machine is to operate in such a manner that soil adjacent the cable channel be disturbed as little as possible. This machine has the form of a two-wheeled attachment mountable to the rear of a towing vehicle and provided with two downwardly extending rippers having wider rear faces and knife-like forward edges, so as to appear wedge-like in horizontal cross section, the two rippers being located one behind the other, considered in the direction of tow, and extending downward into the soil to different respective depths. At their lower ends these rippers have forwardly extending foot-shaped portions that are pointed at their forward ends. The front ripper is shorter than the rear ripper. A dispensing chute for the cable is located rearward of the ripper. Both rippers extend substantially vertically and are mounted on the vehicle frame swingably about horizontal axes. They are formed as two-armed levers whose upper ends are connected via linkages to an eccentric drive in such a manner that the two rippers swing forward and backward in phase opposition to each other, so that the knife-like, vertically extending forward edges of their lower arms both perform generally horizontal motions, in phase opposition to each other, and thus form by cutting the channel into which the cable is to be laid. In addition, eccentric vibrators can impart to the whole frame structure a vibratory motion intended to improve the effectiveness of channel cutting and reduces power consumption. Shares for breaking up and loosening deep subsoil are not provided. The two rippers operate to different depths, so that each need penetrate forwardly only through a subsoil layer corresponding to its own depth of action, and accordingly the rear ripper, operating as it does at a lesser depth, travels through the channel already cut by the front ripper. In this prior-art machine, it is certainly true, in some sense, that two downwardly extending earth-cutting tools are provided and, generally speaking, for earth-working purposes. The arrangement and manner of support of the earth-cutting tools, and the construction of the machine in general, are not such, and not conceived to be such, as to be suitable for loosening compacted, deep-lying subsoil in furrows of the breadths normally required in agriculture.
DE-PS 868,678 discloses a method and an arrangement for reducing the towing force required of a cultivating machine, the machine having a cultivating tool which performs swinging motions. For example a plowshare is suspended by means of a holder from a plurality of springs so as to have two degrees of freedom of swinging motion and is set into and kept in motion by bodies that are rotatably secured to and eccentrically mounted on the holder, in order to reduce friction and comminute larger clumps of soil. The plowshare can be supported directly via flat springs, with the swinging eccentric drive being provided at the free, plowshare-carrying end of the spring. The plowshare cannot execute predetermined, systematic motions controlled with the exactness of a lever arrangement.
U.S. Pat. No. 3,451,487 discloses the use of centrifugal weights for generating vibratory motions in cultivating machines of the type which in their entirety are set into vibratory motion.
The two last-mentioned machines (W. German Patent 868,678 and U.S. Pat. No. 3,451,487) are not provided with plowshare holders exhibiting linkage-action-type motion generation for the plowshares, i.e., such as is provided in the machines discussed further above, and for this reason their plowshares are incapable of following or describing completely predetermined paths of motion. On the other hand, the earlier-discussed machines that do provide for well-defined paths of plowshare or blade motion, if operated to work in deep subsoil, as a rule require very great towing forces that can be provided only by caterpillar-type towing vehicles.
There exists therefore a need for an effective deep-acting, soil-loosening plow which can be practicably towed by a conventional wheeled field tractor.